1. Field of the Invention
The present invention relates to a rewritable recording medium, a recorder and a reproducing device, and more particularly to a recording medium storing the data such as dynamic images, still pictures or voices along with the data recording time information, a recorder and a reproducing device for use with the recording medium.
2. Description of the Related Art
A rewritable recording medium of large capacity such as a DVD-RAM or DVD-RW has appeared in the market, and the recorders and the reproducing devices such as a video recorder/player, an audio recorder/player or a camera, along with the technologies for recording the image or voice data, have been developed. The dynamic image data may be typically the coded data in accordance with an MPEG (Moving Picture Experts Group) method as defined in the ISO/IEC1172 standards or ISO/IEC13818 standards. The still picture data may be typically the intraframe coded data (one picture) in accordance with the MPEG method or the coded data in accordance with an JPEG method as defined in the ISO/IEC10918-1 standards. The voice data may be typically the coded data in accordance with the MPEG method or an LPCM (Linear Pulse Coding Modulation) method. For example, in the case where the still picture data having a data size of about 100 Kbytes is recorded on a DVD-RAM having a capacity of 4.7 giga-bytes on one side, the still picture data of as many as about 47000 sheets (=4.7×1000000/100) can be recorded.
When such data is recorded on a recording medium, it is commonly practiced to record the data together with the recording time information to facilitate data reduction or data retrieval at the time of reproduction. For example, a first recording time management method in which the recording time information is multiplexedly recorded along with the image or voice stream data as disclosed in JP-A-2000-113641 specification, and a second recording time management method in which the management information for managing the image or voice stream data is prepared separately, and the recording time information is collectively recorded in that management information, as disclosed in JP-A-2000-134565 specification (U.S. patent application Ser. No. 09/369,401) were proposed. The first and second recording time management methods that have some merits and demerits as will be described later may be generally employed in combination.
Supposing that the recording medium or recorder is used in all the countries of the world, the time zone information indicating the standard time (or time difference from the reference point of site) of an area where the data is recorded is commonly recorded on the recording medium along with the data or data recording time. In this case, the time zone information is not appended to each data, but the total management information (VMGI) for managing all the data on the recording medium is generally provided, including one time zone information.
If it is supposed that the recording medium is mailed throughout the world, or the recorder is used while moving across the frontier, the standard time which is the reference of the recording time may be changed. At this time, there is a desire that the local time of the area where the data is recorded is left on the recording medium in some way.
Also, there is a desire that the time zone information once recorded is changed.
In this case, along with the change of the time zone information, it is necessary that the recording time information is changed (or corrected for time difference) and recorded again on the recording medium, taking into consideration the time difference before and after change of the time zone. With the first recording time management method, it is required to read all the recording time information from the stream data of large data size, correct for time difference and record it again, and this is unpractical in respect of the processing time. On the other hand, with the second recording time management method, all the recording time information is managed singly in the management information, whereby the correction for time difference is easy. However, if the recording time information for all the data is carried in the management information, the management information size becomes large, as described in JP-A-2000-134565 specification. Therefore, generally, the recording time information for part of the data is carried in the management information, and the remaining data is in accordance with the first recording time management method. Accordingly, with the prior art, it is difficult to effect the change of the time zone and the correction for time difference of the data recording time information in a short time without causing any inconsistency in the recording time information between the management information and the stream data.
Also, once the time zone information which is managed in the total management information (VMGI) on the recording medium is changed, the user inconveniently can not know the time (local time) in the area where individual data is recorded.
If the time zone is not changed to prevent such inconsistency, the local time (current time) at the destination of foreign country in travel which the user knows and the time displayed by the recorder/reproducing device are not consistent owing to a time difference, which is less user friendly or inconvenient for the user.
It is an object of the present invention to record the relation between the local standard time and the time zone information of a disk on a recording medium in some format of recording, when the user mails the recording medium to the world over or employs a recorder while moving across the frontier.
It is another object of the invention to provide a recording medium, and a recorder and a reproducing device for use with the recording medium, wherein the recording medium is able to implement a data management method capable of changing the time zone information and correcting the data recording time information for time difference in a short time without causing any inconsistency in the recording time information between the management information and the stream data, or a data management method for reconstructing the local time after changing the time zone, or a data management method for correcting for time difference without changing the time zone.